Hiding information out-of-phase in color channels

- Digimarc Corporation

The present invention relates to steganographically hiding images and information. In a preferred embodiment, an image is hidden within a media signal. The media preferably includes a cyan (C) color plane, a magenta (M) color plane, a yellow (Y) color plane and a black (K) color plane. In an alternative embodiment, the media includes a spot color. The image is converted into a black color channel image and is then applied to the media's K channel. The black channel image is inverted and the inverted image is applied to the media's CMY (or spot) color planes.

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Description
RELATED APPLICATION DATA

This application is a continuation in part of U.S. patent application Ser. No. 09/945,243, filed Aug. 31, 2001 and now U.S. Pat. No. 6,718,046. The Ser. No. 09/945,243 application is a continuation in part of U.S. patent application Ser. No. 09/933,863, filed Aug. 20, 2001 and now U.S. Pat. No. 6,763,123. The Ser. No. 09/933,863 application is a continuation in part of U.S. patent application Ser. No. 09/898,901, filed Jul. 2, 2001 and now U.S. Pat. No. 6,721,440 which is a continuation in part of U.S. patent application Ser. No. 09/553,084, filed Apr. 19, 2000 and now U.S. Pat. No. 6,590,996. This application is also a continuation in part of U.S. patent application Ser. No. 10/094,593, titled “Identification Document Including Embedded Data”, filed Mar. 6, 2002 (published as US 2002-0170966 A1), which claims the benefit of U.S. Provisional Application Ser. No. 60/356,881, filed Feb. 12, 2002. This application is also related to U.S. patent application Ser. Nos. 10/115,441 now U.S. Pat. No. 6,804,377 and 10/115,582 (published as US 2002-0164052 A1), filed concurrently herewith. Each of the above U.S. patent applications is herein incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to hiding data, and is particularly illustrated with reference to hiding information out-of-phase in color channels.

BACKGROUND AND SUMMARY OF THE INVENTION

The above mentioned parent applications disclose various techniques for embedding and detecting out-of-phase digital watermarks.

Digital watermarking technology, a form of steganography, encompasses a great variety of techniques by which plural bits of digital data are hidden in some other object, preferably without leaving human-apparent evidence of alteration.

Digital watermarking may be used to modify media content to embed a machine-readable code into the media content. The media may be modified such that the embedded code is imperceptible or nearly imperceptible to the user, yet may be detected through an automated detection process.

Digital watermarking systems typically have two primary components: an embedding component that embeds the watermark in the media content, and a reading component that detects and reads the embedded watermark. The embedding component embeds a watermark pattern by altering data samples of the media content. The reading component analyzes content to detect whether a watermark pattern is present. In applications where the watermark encodes information, the reading component extracts this information from the detected watermark. Assignee's U.S. patent application Ser. No. 09/503,881 (now U.S. Pat. No. 6,614,914), filed Feb. 14, 2000, discloses various encoding and decoding techniques. U.S. Pat. Nos. 5,862,260 and 6,122,403 disclose still others. Each of these U.S. patent documents is herein incorporated by reference.

Now consider our inventive out-of-phase digital watermarking techniques with reference to FIGS. 1a and 1b. In FIG. 1a, the dash/dot C, M, Y and K lines represent, respectively, cyan, magenta, yellow and black color channels for a line (or other area) of a media signal (e.g., a picture, image, media signal, document, etc.). The FIG. 1a lines represent a base level or a particular color (or gray-scale) level (or intensity). Of course, it is expected that the color (or gray-scale) level will vary over the media signal. FIG. 1b illustrates the media of FIG. 1a, which has been embedded with an out-of-phase digital watermark signal. The watermark signal is preferably applied to each of the color component dimensions C, M and Y.

In FIGS. 1a and 1b, the M and Y channels are represented by one signal, since these color components can be approximately equal, but separate signals. Of course, it is not necessary for these components to be equal, and in many cases the yellow and magenta components are not equal. The illustrated “bumps” (or “tweaks”) in FIG. 1b represent the digital watermark signal, e.g., upward and downward signal adjustments in relation to a respective color channel at given points over the media signal. The tweaks are preferably applied at the same level (or signal strength). Alternatively, the bumps are applied with a different signal strength (or tweak level) when compared to one another. Of course, these tweaks can be embedded over a color channel in a predetermined pattern, a pseudo random fashion, a random fashion, etc., to facilitate embedding of a digital watermark signal.

For the K dimension (or channel), the digital watermark signal is preferably embedded to be out-of-phase with respect to the CMY channels. Most preferably, the K channel is approximately 180 degrees out-of-phase (e.g., inverted) with the watermark signals in the CMY color channels, as shown in FIG. 1b. For example, if a digital watermark signal modifies each of the color channels at a media first location with a tweak level of say 7, then a tweak level of −7 correspondingly modifies the K channel at the media's first location. This inventive digital watermark technique is referred to as our out-of-phase (or “K-phase”) digital watermark. (We note that if a watermark signal is determined in terms of luminance, we can assign or weight corresponding tweak levels to the respective color plane pixel values to achieve the luminance value tweak. Indeed, a tweak can be spread over the CMY channels to achieve a collective luminance at a given media location. The luminance attributable to the CMY tweak is preferably cancelled or offset by the luminance effect attributable to a corresponding inverted K channel tweak at the give media location.).

Our inventive watermarking scheme greatly reduces watermark perceptibility. Since the watermark signal for the K channel is applied approximately 180 degrees out-of-phase, when compared to the respective tweaks applied to the C, M and/or Y channels, the watermark visibility is greatly reduced. The visibility reduction is achieved by the effective cancellation of perceived luminance changes when the CMYK image is viewed or printed. Indeed, combining an inverted watermark signal “tweak” or “bump” in a K channel with a corresponding non-inverted watermark signal tweak or bump in the CMY channels effectively cancels an overall perceived luminance change for a given area (e.g., a pixel or block of pixels)—greatly reducing visibility of the digital watermark.

The present invention discloses a new data hiding technique based on our out-of-phase technology. According to one implementation of the present invention, an image is hidden in or carried by a media signal. The hiding is accomplished with our out-of-phase embedding techniques. The image can be a photograph, a graphic, a barcode (1-D or 2-D), etc., etc. Another aspect of our inventive techniques is used to improve the visibility characteristics of our out-of-phase embedding techniques.

The foregoing and other aspects, features and advantages of the present invention will be even more apparent from the following detailed description, which proceeds with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a diagram illustrating CMYK channels.

FIG. 1b illustrates the color CMYK channels of FIG. 1a, embedded with information.

FIG. 2 illustrates hiding an image in media.

FIG. 3 is a flow diagram illustrating an embedding method according to one implementation of the present invention.

FIGS. 4 and 5 are graphs showing hidden signal strength in terms of luminance.

FIGS. 6 and 7 are graphs showing hidden signal strength in terms of color saturation.

FIG. 8 illustrates limiting a signal tweak in low CMY areas to reduce hidden signal visibility.

FIG. 9 illustrates the segmentation of media into blocks.

FIG. 10 illustrates a feedback loop in an embedding process.

FIG. 11 illustrates feedback for the FIG. 10 feedback loop.

FIGS. 12a and 12b illustrate detection apparatus.

FIG. 13 illustrates orientation fiducials hidden in a media signal with our out-of-phase embedding techniques.

FIG. 14 illustrates out-of-phase embedding of a spot color.

FIG. 15 illustrates a printer calibration process.

 DETAILED DESCRIPTION

Image Embedding

With reference to FIG. 2, an image 10 is steganographically hidden within media 12. Of course, media 12 may represent digital media such as an image, photograph, video frame, graphic, picture, logo, product tag, product documentation, visa, business card, art work, brochure, document, product packaging, trading card, banknote, deed, poster, ID card (including a driver's license, member card, identification card, security badge, passport, etc.), postage stamp, etc., etc. And image 10 can correspond to a digital representation of a photograph, picture, graphic, text, orientation fiducial, object, barcode, message, digital watermark, outline, symbol, etc., etc. In the FIG. 2 example, image 10 includes a close-up photograph, and the media includes a driver's license or passport photograph. The hiding (or embedding) is accomplished using our inventive out-of-phase techniques.

With reference to FIG. 3, our K-phase hiding is preferably initiated by converting image 10 to a black channel image 10′ (step 30—FIG. 3). Most digital imaging software tools such as Adobe's Photoshop facilitate such a black channel conversion. The black channel image 10′ includes a set of black pixel values (e.g., gray-scale values) 10′. A location in the media 12 is selected to place the black channel image (step 32). The dashed circle 13 in FIG. 2 represents this selected location. The media 12 location can be represented by sets of media 12 pixels. (For example, a first set of pixels corresponds to the selected location's black channel values, a second set corresponds to the selected location's cyan channel values, a third set corresponds to the selected location's magenta channel values, and a fourth set corresponds to the selected location's yellow channel values.). The set of black channel image 10′ values is applied to the black channel pixels in the selected location of media 12—effectively modifying media 12 (step 34). For example, if an image 10′ pixel includes a gray-scale value of 3, this gray-scale value is applied to a corresponding pixel in the selected media 12 location to raise that corresponding pixel value by 3. In an alternative implementation, instead of adjusting the corresponding pixel in the selected media 12 location by the gray-scale value, we replace that corresponding pixel value with the black image 10′ gray-scale value. In another implementation, the corresponding media 12 pixel is modified to achieve the gray-scale value of the image 10′ pixel. Of course we can scale and/or weight the gray-scale value as needed prior to modifying pixels in the selected location of media 12.

The black channel image 10′ is inverted to produce a set of signal tweaks (step 36). For example, if a black channel pixel is tweaked by a grayscale value of say 24, then a corresponding, inverted CMY tweak value is −24. (As an alternative implementation, image 10 is converted into corresponding C, M and Y images and such images are applied to their respective channels. These signal tweaks are then used to modify or change the color values in their respective CMY color channels (step 38). Most preferably, in the above example, the −24-tweak value is applied to each of the CMY color channels. The overall luminance cancellation can be effected as such. In another implementation we unevenly spread the tweak value over the CMY channels to achieve an overall luminance change in a given media location to cancel the +24 tweak in the black channel. For example, if using a luminance equation of: L=0.3*C+0.6*M+0.1*Y, we can achieve an overall luminance tweak of −24 by tweaking C=−15, M=−30 and Y=−15. Of course there is a vast range of other color combinations to achieve the same collective luminance change. Care should be taken, however, to minimize a color shift when using this tweak-spreading alternative. The CMY pixels and the K pixels are thus out-of-phase with respect to one another—resulting in a local cancellation of the perceived luminance change. Accordingly, image 10 is successfully hidden or carried by media 12.

The selected location 13 can be determined manually, e.g., via editing software tools (like Adobe's Photoshop). Or the selection process can be automated.

Image Hiding Enhancements

We have developed improvements to enhance our out-of-phase hiding techniques. These improvements apply to hiding both images and digital watermark signals (in this section both will be referred to as a hidden signal). While these techniques are not necessary to carry out our out-of-phase hiding techniques, they generally reduce the visibility of a hidden signal. Consider our following inventive improvements.

High Luminance Areas

Media 12 may include areas of low CMY and/or K ink (or signal intensity). In a first case, an area includes little or no C, M and/or Y ink. This results in an inability to counteract (or cancel) an inverted signal in a corresponding channel(s). Accordingly, we can sample the luminance of a media 12 area (or pixel) and, based on the luminance level, determine whether to scale back the hidden signal strength. For example, we begin to scale back the signal strength once the luminance reaches a predetermined threshold (e.g., in a range of 70-95% luminance). We can scale back the signal strength for a given area according to a linear reduction, as shown in FIG. 4, or we can scale the signal strength in a non-linear manner, e.g., as shown in FIG. 5. The illustrated scaling signal strength applies to both the K channel and CMY channels. In a related implementation, we determine the luminance of the yellow channel. We base our scaling decisions on the yellow luminance percentage.

Saturated Color

Hiding signals in a saturated color area can also result in increased hidden signal visibility concerns. For this document the term “saturation” refers to how pure a color is, or refers to a measure of color intensity. For example, saturation can represent the degree of color intensity associated with a color's perceptual difference from a white, black or gray of equal lightness. We determine the color saturation level in a color plane (e.g., the yellow color plane), and then scale back a hidden signal strength as the color saturation level exceeds a predetermined level (e.g., 80% yellow color saturation). As with the FIGS. 4 and 5 implementations, we can scale the signal strength in a linear manner (FIG. 6) or in a non-linear manner (FIG. 7).

Low or High Luminance Areas

We have found that we can even further improve the visibility characteristics of our hidden signals by considering the amount of luminance at a given pixel or other media 12 area. A low luminance may indicate that there is insufficient CMY to compensate for a K channel tweak. For example, a 10% luminance in CMY for a given pixel implies that the pixel can accommodate only about a 10% signal tweak (e.g., remember the simplified luminance relationship mentioned above: L=0.3*C+0.6*M+0.1*Y). With reference to FIG. 8, we can cap (or limit) the positive K tweak signal level in such low CMY areas to ensure that the CMY levels can be sufficiently decreased to counteract or cancel the positive K channel signal.

Similarly, in an area of high CMY luminance, a negative K channel tweak can be capped (or limited) to ensure a sufficient range to increase the CMY values.

Equalizing Detectability

Now consider an implementation where media 12 is segmented into a plurality of blocks (FIG. 9). Here a block size can range from a pixel to a group of pixels. We redundantly embed an image or watermark signal in each of (or a subset of) the blocks. As shown in FIG. 10, we preferably use signal feedback (k) to regulate the embedding process. A signal feedback (k) method is shown in FIG. 11. A black (K) channel image or watermark signal (in this section hereafter both referred to as a “watermark”) is embedded in block i of media 12 (step 110), where “i” is an integer ranging from 1-n and where n is the total number of blocks. The watermark signal is inverted (step 112) and embedded in the CMY channels of block i (step 114). At this point, we preferably perform a detection process of the signal embedded within the ith block (step 116). The detection process determines whether the signal is sufficiently detectable (step 118). The term “sufficient” in this context can include a plurality of levels. In one, “sufficient” implies that the signal is detectable. In another, the detectability of the signal is ranked (e.g., according to error correction needed, ease of detectability, or a detection-reliability metric, etc.). The term sufficient in a ranking context also implies that the detection ranking is above a predetermined threshold. The process moves to embed a new block i+1 if the embedding is sufficient (120). Otherwise the signal strength is increased or otherwise altered (step 122) and the embedding of block i is repeated.

Such a signal feedback process helps to ensure consistent embedding throughout media 12.

Infrared Image Detection

An infrared detection method is illustrated with reference to FIG. 12a. In particular, the illustrated detection method employs infrared illumination to facilitate image (or watermark) detection. Media 12 is illuminated with an infrared illumination source 14. The media 12 is embedded as discussed above, for example, to include various components in a multicolor dimension space (e.g., CMYK). A first component (or image) is preferably embedded in the CMY channels. A second component (or image) is embedded in the K channel. The second component is preferably inverted (or is out-of-phase) with respect to the CMY channels.

Infrared illumination source 14 preferably includes a light emitting diode, e.g., emitting approximately in a range of 800 nm-1400 nm, or a plurality of light emitting diodes (“LED”). Of course, there are many commercially available infrared diodes, and such may be suitable used with our present detection techniques. It will be appreciated that many commercially available incandescent light sources emit light both in the visible and infrared (“IR”) spectrums. Such incandescent light sources may alternatively be used as infrared illumination source 14. Indeed, infrared watermark detection may be possible in otherwise normal (“daylight”) lighting conditions, particularly when using an IR-pass filter.

A conventional power source powers the infrared illumination source. (We note that a variable trim resistor and a small wall transformer can be optionally employed to control illumination source 14.). Power alternately can be supplied from a battery pack, voltage or current source, or by directly tapping a power source of a camera, e.g., internally drawn from a parallel, USB, or corded power lines. For a consumer device, a battery pack or a single power cord that is stepped down inside a digital watermark reader housing can also be used.

Returning to the composition of an out-of-phase hidden image (or watermark), a first image (or watermark) component is embedded in a K (or black) channel. A second image component, e.g., which is out-of-phase with respect to the K channel, is embedded in the CMY channels. These characteristics have significance for infrared detection. In particular, C, M and Y inks will typically have high transmission characteristics in the infrared spectrum when printed, which render them nearly imperceptible under infrared illumination. Yet conventional black inks absorb a relatively high amount of infrared light, rendering the black channel perceptible with infrared illumination. We note that standard processing inks, such as those conforming to the standard web offset press (SWOP) inks, include black ink with IR detection properties. Of course, there are many other inks that may be suitably interchanged with the present invention.

As discussed above our out-of-phase embedding provides an effective cancellation of perceived luminance changes when the CMYK image is viewed in the visible spectrum. Indeed, combining an inverted watermark signal “tweak” or “bump” in a K channel with a corresponding non-inverted watermark signal tweak or bump in the CMY channels effectively cancels an overall perceived luminance change. However, under infrared illumination, the hidden image (or watermark) component in the black (K) channel becomes perceptible without interference from the C, M and Y channels. An infrared image primarily portrays (e.g., emphasizes) the black channel, while the C, M and Y channels are effectively imperceptible under infrared illumination.

In one implementation, camera 16 captures an image of media 12. Preferably, camera 16 includes an IR-Pass filter that passes IR while filtering visible light. For example, the Hoya RM90 filter available from M&K Optics L.L.C. is one of many IR-Pass/Visible Opaque filters suitable for daylight detection. Another suitable filter is the RG850 filter, part number NT54-664, available from Edmund Scientific. These filters are offered as examples only, and certainly do not define the entire range of suitable IR-pass filters. Of course there are many other IR-Pass filters that are suitably interchangeable with the present invention.

In yet another implementation, a conventional digital camera (or web cam) is modified so as to capture infrared light. In particular, most digital cameras and web cams include an IR filter, which filters out IR light. Removing the IR filter allows the camera to capture light in the IR spectrum. Consider a visibly dark environment (e.g., an enclosed case, shielded area, dark room, etc.). Media 12 is illuminated by infrared illumination source 14 in the visibly dark environment. Camera 16 (without an IR filter) effectively captures an infrared image (i.e., the K channel image) corresponding to the illuminated media 12.

The captured image is communicated to computer 18. Preferably, computer 18 includes executable software instructions stored in memory for execution by a CPU or other processing unit. If media 12 includes a digital watermark, the software instructions preferably include instructions to detect and decode the embedded digital watermark. Otherwise, the instructions preferably include instructions to display the K-phase image. The software instructions can be stored in memory or electronic memory circuits. Of course, computer 18 can be a handheld computer, a laptop, a general-purpose computer, a workstation, etc. Alternatively, computer 18 includes a hard-wired implementation, which precludes the need for software instructions.

With reference to FIG. 12b, a detection housing 20 can be provided to house an infrared illumination source 14 and digital camera (both not shown in FIG. 12b, since they are within the opaque housing 20). The housing 20 is preferably opaque to shield (or otherwise constructed to filter) the camera and media 12 from visible light. The housing 20 has an opening 20a to receive the media 12. In a first case, opening 20a is adapted to engulf media 12. This allows media 12 to be placed on a surface (e.g., table, imaging station, or counter) and the housing opening 20a to be placed over media 12, effectively shielding media 12 from visible light. In a second case, the opening 20a receives media 12 into (e.g., slides media through opening 20a) and positions media 12 within the opaque housing 20. In either implementation, the infrared illumination source 14 illuminates media 12, and the digital camera 12 captures an image of the illuminated media (e.g., captures as image of the K-channel image). The digital camera 12 communicates with computing device 14, which detects and decodes a digital watermark embedded with media 12, if present, or otherwise displays the image.

In another illustrative embodiment, the above described infrared detection technique is carried out in a visibly dark environment, such as a dark room, shielded area, etc. An out-of-phase image (or digital watermark) is embedded in media. The media is illuminated with an infrared illumination source, and a digital camera captures an image of the illuminated media.

In still another illustrative embodiment, the above described infrared detection technique is carried out in a visibly lighted environment. An out-of-phase image (or watermark) is embedded in media. The media is illuminated with an infrared illumination source, and a digital camera captures an image of the media. Preferably, the camera includes an IR-pass filter. The digital camera communicates with a computing device, which detects and decodes an out-of-phase image (or digital watermark) embedded in the media.

Infrared detection is an elegant solution to detect out-of-phase images or digital watermarks, since high transmission colors in the IR spectrum are effectively washed out, allowing detection of a low transmission color channel. Specialized inks are not required to embed the out-of-phase digital watermark. Indeed most multicolor printer ink packs, offset ink, process inks, dye diffusion thermal transfer inks, such as inks conforming to the SWOP standard include black inks that allow infrared detection. Some of these inks include a carbon-based black ink, furthering the absorption of IR. While infrared detection is ideal for out-of-phase images or digital watermarks, this method is also applicable to detection of conventional digital watermarks. For instance, a watermark signal can be embedded only in a black channel of media. Infrared illumination helps to reveal the embedded watermark in this black channel. Alternatively, a digital watermark is embedded across many color planes, while detection is carried out in only those color planes that are perceptible with IR illumination. Additionally, while we have discussed infrared detection techniques, we note that ultraviolet (UV) detection is also possible. In this case, one of the color channels (including the K channel) preferably includes UV pigments or properties. A UV detection process is carried out in a manner analogous to that discussed above. (We also note that a CMY color can include IR/UV pigments or properties to facilitate detection of that color with respective IR or UV detection methods.).

Applications

Now consider a few applications of our inventive out-of-phase hiding techniques.

Identification Documents (e.g., Passports, Driver's Licenses, etc.)

An out-of-phase image is hidden in an identification document to provide enhanced security. For example, a hidden image is a gray-scale version of the identification document's photograph. An airport screener, or law enforcement officer, illuminates the out-of-phase image with infrared (or ultraviolet) light for comparison of the hidden image to the printed photograph. Or, instead of a photograph, the hidden image may include text, which can be compared with the visibly printed text on the identification document.

In assignee's U.S. application Ser. No. 10/094,593 (published as US 2002-0170966 A1), we disclosed various security and authentication improvements. One disclosed improvement ties machine-readable code such as barcode information to a digital watermark. Our inventive out-of-phase hiding techniques can be used with the techniques disclosed in the above-mentioned application. For example, instead of hiding an out-of-phase image in the identification document, we instead embedded an out-of-phase digital watermark. The digital watermark includes a payload, which has information corresponding to the printed information or to information included in a barcode. In one implementation, the information includes a hash of the barcode information. In another implementation, we hid a barcode in the identification document as discussed below.

Hiding Bar Codes in Out-of-Phase Channels

Over the years, a number of standards organizations and private entities have formed symbology standards for bar codes. Some examples of standards bodies include the Uniform Code Council (UCC), European Article Numbering (EAN, also referred to as International Article Numbering Association), Japanese Article Numbering (JAN), Health Industry Bar Coding Counsel (HIBC), Automotive Industry Action Group (AIAG), Logistics Application of Automated Marking and Reading Symbols (LOGMARS), Automatic Identification Manufacturers (AIM), American National Standards Institute (ANSI), and International Standards Organization (ISO).

The UCC is responsible for the ubiquitous bar code standard called the Universal Product Code (UPC). AIM manages standards for industrial applications and publishes standards called Uniform Symbology Standards (USS). Some well know bar code schemes include UPC and UCC/EAN-128, Codabar developed by Pitney Bowes Corporation, I 2 of 5 and Code 128 developed by Computer Identics, Code 39 (or 3 of 9) developed by Intermec Corporation, and code 93.

Some bar codes, such as UPC, are fixed length, while others are variable length. Some support only numbers, while others support alphanumeric strings (e.g., Code 39 supports full ASCII character set). Some incorporate error checking functionality.

While the bar codes listed above are generally one-dimensional in that they consist of a linear string of bars, bar codes may also be two-dimensional. Two dimensional bar codes may be in a stacked form (e.g., a vertical stacking of one-dimensional codes), a matrix form, a circular form, or some other two-dimensional pattern. Some examples of 2D barcodes include code 49, code 16k, Data Matrix developed by RVSI, QR code, micro PDF-417 and PDF-417.

For more information on bar codes, see D. J. Collins, N. N. Whipple, Using Bar Code-Why It's Taking Over, (2d ed.) Data Capture Institute; R. C. Palmer, The Bar Code Book, (3rd ed.) Helmers Publishing, Inc., and P. L. Grieco, M. W. Gozzo, C. J. Long, Behind Bars, Bar Coding Principles and Applications, PT Publications Inc., which are herein incorporated by reference.

A hidden, out-of-phase image can include a barcode. Consider the vast possibilities. A barcode is often disdained for aesthetic reasons, but a hidden, out-of-phase barcode can carry relatively large amounts of information while remaining virtually imperceptible. In one implementation, a barcode is redundantly hidden or titled throughout media using our out-of-phase embedding techniques. This allows for robust barcode detection even if only a portion of the media is recoverable. In another implementation one or more barcodes are placed in predetermined areas throughout the image. In still another implementation, a barcode reader, such as those provided by Symbol (e.g., the VS4000 and P300IMG models) or Welch Allyn (e.g., the Dolphin model), is augmented with an infrared illumination source and/or IR-filters. Once illuminated, the barcode reader detects and decodes a barcode hidden in a K channel.

Fiducials and Orientation Signal

In some digital watermarking techniques, the components of the digital watermark structure may perform the same or different functions. For example, one component may carry a message, while another component may serve to identify the location or orientation of the watermark in a signal. This orientation component is helpful in resolving signal distortion issues such as rotation, scale and translation. (Further reference to orientation signals can be made, e.g., to previously mentioned application Ser. No. 09/503,881.). In some cases, channel capacity is congested by an orientation signal.

One improvement is to embed an orientation signal using our out-of-phase hiding techniques. The message component of a digital watermark can then be embedded using out-of-phase or non-out-of-phase embedding techniques. This improvement will increase message capacity, while improving visibility considerations. Scale, orientation, and image translation can be resolved based on the orientation of the fiducial.

A related improvement embeds a plurality of fiducials or orientation markers 54 in an out-of-phase channel of media 12 (FIG. 13). A watermark detection module detects the fiducials to identify distortion.

Spot Colors

We have found that our inventive techniques are not limited to process colors. Indeed, our out-of-phase techniques can be extended to spot colors. (See Assignee's U.S. patent application Ser. No. 10/074,677, filed Feb. 11, 2002, for a further discussion of spot colors and digitally watermarking spot colors. The Ser. No. 10/074,677 application is herein incorporated by reference.). With reference to FIG. 14, and preferably (but not limited to) relatively darker spot colors, e.g., violets, blues, etc., we counteract a watermark signal (or image) embedded in the spot color channel with an inverted signal in a K channel. Preferably, the K channel base intensity is subtle (e.g., 0% as represented by the K channel base level dashed line in FIG. 14) in comparison to the base level spot color intensity (e.g., 100% intensity as represented by the spot color maximum level dashed line in FIG. 14). The watermark signal (or image) signal is embedded through a combination of negative spot color tweaks and positive, offsetting, K channel tweaks. Infrared illumination facilitates detection of the K-channel watermark tweaks. (Embedding a spot color need not be limited to negative tweaks. Indeed, if the spot color is not at 100% intensity, positive spot color tweaks and corresponding negative K channel tweaks can facilitate embedding.).

Paper Information and Printing Processes

Another improvement is to carry printing process information and/or paper characteristics with a digital watermark. For example, a digital watermark may include signal gain or embedding characteristics that are specific to a printing press, printing process, process ink type or paper characteristics. The digital watermark can be embedded in a digital file, which is analyzed prior to a print run. The embedding process is adjusted according to the watermark data. Or the watermark signal can be analyzed after printing one or more test copies. The signal strength or payload metric can be analyzed to determine whether the process should be adjusted.

Our out-of-phase digital watermark can be used to detect a misalignment in a printing process. With reference to FIG. 15 a printer 150 outputs a CMYK (or spot color, etc.) printed sheet 152. The printed sheet includes an out-of-phase digital watermark or image hidden therein. An input device 154 captures an image of sheet 152. Preferably, input device 154 captures a visible spectrum image of sheet 152. The input device provides the captured image (e.g., digital scan data) to a watermark detector 156. The watermark detector 156 analyzes the captured image in search of the embedded out-of-phase digital watermark. The watermark detector 156 should not be able to detect the embedded watermark if the printing of the CMY and K are aligned, due the localized cancellation of the signal tweaks (or luminance changes). The term aligned in this context implies that the CMY and K are sufficiently inverted to allow localized cancellation. A misalignment is identified if the watermark detector 156 reads the digital watermark. Such a misalignment is optionally communicated from the watermark detector 156 to the printer 150 or otherwise provided to announce the printing misalignment. Of course other alignment and color balance information can be identified from the detection of the digital watermark.

Color Channel Keys

A related inventive technique embeds a key in one color channel for decoding a watermark in a second color channel. Consider an implementation where a first digital watermark is embedded in a first color channel. The first digital watermark includes a payload including a key. The key is used to decode a digital watermark embedded in a second color plane. The term decode in this context includes providing a reference point to locate the second watermark, providing a key to unlock, decrypt, decode or unscramble the second digital watermark payload, etc. Of course this inventive technique is not limited to our out-of-phase digital watermarks.

Fragile Security

Our out-of-phase hiding techniques are fragile since a signal processing operation that combines the K channel with the CMY channels effectively cancels the hidden signal. A fragile watermark is one that is lost or degrades predictably with signal processing. Conversion to other color spaces similarly degrades the watermark signal. Take a typical scan/print process for example. Digital scanners typically have RGB image sensors to measure the image color. Scanning an out-of-phase embedded CMYK image degrades the embedded watermark due to the combination of K with CMY in a local area, effectively canceling the watermark. When the RGB image representation is converted to CMYK and printed, the watermark signal is effectively lost. Similarly, other conversions, such as to a L*a*b color space, degrade the out-of-phase watermark due to the combination of K with CMY throughout local areas. Nevertheless, the watermark signal is detectable from an original CMYK media, since the K channel can be detected separately by viewing, e.g., in the near infrared.

A fragile watermark has utility in many applications. Take counterfeiting, for example. The inventive fragile watermark is embedded in original CMYK media. If the media is copied, the embedded fragile watermark is either lost or degrades predictably. The copy is recognized as a copy (or counterfeit) by the absence or degradation of the fragile watermark. Fragile watermarks can also be used in conjunction with other watermarks, such as robust watermarks. The fragile watermark announces a copy or counterfeit by its absence or degradation, while the other robust watermark identifies author, source, links and/or conveys metadata or other information, etc. In other embodiments, a fragile watermark is an enabler. For example, some fragile watermarks may include plural-bit data that is used to enable a machine, allow access to a secure computer area, verify authenticity, and/or link to information. This plural-bit data is lost or sufficiently degrades in a copy, preventing the enabling functions.

Another inventive feature is to embed a hash or other representation of a product (e.g., product code or serial number) in a digital watermark payload or message. The digital watermark is then tied or linked directly to the product. If the product includes a barcode having the product code, such can be compared with the digital watermark.

Conclusion

Preferably, an out-of phase watermark signal is embedded 180 degrees out-of-phase with corresponding channels. However, some cancellation will still be achieved if the signal is approximately 180 degrees, for example, in a range of ±0-50% from the 180-degree mark. The term “inverted” includes values within this range. We note that while the present invention has been described with respect to CMYK process inks, the present invention is not so limited. Indeed, our inventive techniques can be applied to printing processes using more than four inks with the K channel canceling the three or more color channels. Similarly, as shown above under the spot color discussion, our inventive techniques are also applicable to printing processes using less than four inks. Of course our techniques can be used with a variety of printing techniques, including offset printing, dye diffusion thermal transfer (D2T2), other thermal transfers, process ink printing, etc., etc., etc.

The section headings in this application are provided merely for the reader's convenience, and provide no substantive limitations. Of course, the disclosure under one section heading may be readily combined with the disclosure under another section heading.

To provide a comprehensive disclosure without unduly lengthening this specification, the above-mentioned patents and patent applications are hereby incorporated by reference, along with U.S. patent application Ser. No. 09/694,465, filed Oct. 22, 2000. The particular combinations of elements and features in the above-detailed embodiments are exemplary only; the interchanging and substitution of these teachings with other teachings in this application and the incorporated-by-reference patents/applications are also contemplated.

The above-described methods and functionality can be facilitated with computer executable software stored on computer readable media, such as electronic memory circuits, RAM, ROM, magnetic media, optical media, memory sticks, hard disks, removable media, etc., etc. Such software may be stored and executed on a general purpose computer, or on a server for distributed use. Data structures representing the various luminance values, out-of-phase embedded signals, embedded color planes, color signals, data signals, luminance signals, etc., may also be stored on such computer readable media. Also, instead of software, a hardware implementation, or a software-hardware implementation can be used.

In view of the wide variety of embodiments to which the principles and features discussed above can be applied, it should be apparent that the detailed embodiments are illustrative only and should not be taken as limiting the scope of the invention. Rather, we claim as our invention all such modifications as may come within the scope and spirit of the following claims and equivalents thereof.

Claims

1. A method of steganographically hiding a first image in a second image, the second image comprising at least a cyan (C) color channel, a magenta (M) color channel, a yellow (Y) color channel and a black (K) color channel, said method comprising:

providing a first set of signal modifications corresponding to the first image;
modifying the K color channel with the first set of signal modifications;
providing a second set of signal modification corresponding to the first image, the second set of signal modifications being inverted with respect to the first set of signal modifications; and
modifying the C, M and Y color channels with the second set of signal modifications.

2. The method of claim 1, further comprising providing a print of the second image once the first image has been hidden therein, wherein the CMY color channel modifications are inverted with respect to the K channel modifications so as to reduce the first image's visibility in the print by canceling perceived luminance change in local areas throughout the print.

3. The method of claim 1, wherein the first image comprises at least one of a photograph, bar code, text, an orientation reference for alt least one of the first and second image, and a digital watermark.

4. The method of claim 3, wherein the first image comprises a barcode, which is redundantly embedded throughout the second image.

5. A method of embedding a digital watermark component in a signal having a plurality of channels, said method comprising:

embedding the digital watermark component in a first of the plurality of channels; and
embedding the digital watermark component in a second of the plurality of channels to be out-of-phase with respect to the digital watermark component in the first channel.

6. The method according to claim 5, wherein the plurality of channels comprises color channels and at least one black channel.

7. The method according to claim 6, wherein the color channels comprise cyan, magenta and yellow.

8. The method according to claim 7, further comprising the steps of embedding the digital watermark component in at least a third channel and a fourth channel.

9. The method according to claim 7, wherein the first channel, third channel and fourth channel respectively comprise the cyan, magenta and yellow, and the second channel comprises black.

10. The method according to claim 5, wherein embedding the digital watermark component in a second of the plurality of channels to be out-of-phase with respect to the digital watermark component in the first channel cancels a perceived luminance change in local areas throughout the signal.

11. The method according to claim 9, wherein for at least one signal area each black channel digital watermark component is inverted with respect to a corresponding digital watermark component of a same level in the cyan, magenta and yellow channel.

12. The method according to claim 9, wherein luminance attributable to at least one black channel digital watermark component is cancelled by a luminance change attributable to a corresponding digital watermark component in the cyan, magenta and yellow channels.

13. The method of claim 12, wherein an embedding level of the digital watermark component varies between each of the cyan, magenta and yellow channels.

14. A method of hiding a first image in a second image comprising:

converting the first image to a black channel image;
selecting a location in the second image to hide the black channel image;
modifying the black channel in the selected location to accommodate the black channel image;
providing in terms of at least cyan, magenta and yellow channels a color channel image that is inverted with respect to the black channel image;
modifying the cyan, magenta and yellow channels in the selected location to accommodate the color channel image.

15. The method of claim 14, wherein an effect of inverting the color channel image with respect to the black color image is to counter-balance luminance changes in local areas throughout the selected area.

16. A method of steganographically embedding a bar code in an image, the image including at least a black channel and at least a color channel, said method comprising:

converting the barcode into a set of grayscale values;
in at least one region of the image, modifying the black channel in the region to accommodate the set of grayscale values;
inverting the grayscale values in the set; and
modifying the color channel in the region to accommodate the inverted grayscale values in a manner so that the modified black channel region is inverted with respect to the modified color channel.

17. The method of claim 16, wherein the color channel comprises a spot color.

18. The method of claim 16, wherein the color channel comprises at least a cyan channel, a magenta channel and a yellow channel.

19. The method of claim 18, wherein said modifying the color channel in the region modifies each of the cyan, magenta and yellow channels to accommodate the inverted grayscale values.

20. The method of claim 16, wherein modifying the black channel region to be inverted with respect to the modified color channel offsets, a luminance change in the region that is attributable to modifications of the color channel.

21. A method of embedding a digital watermark component in a signal having a plurality of channels, said method comprising:

embedding a first digital watermark component in a first of the plurality of channels; and
embedding a second digital watermark component in a second of the plurality of channels,
wherein the first component and the second component cooperate to reduce perceptibility of the digital watermark as embedded in the signal.

22. The method of claim 21, wherein the second component cooperates with the fist component by offsetting localized changes in luminance due to the first component.

23. A method of hiding a first image in a second image comprising:

converting the first image to a black channel image;
selecting a location in the second image to hide the black channel image;
modifying the black channel in the selected location to accommodate the black channel image;
providing in terms of at least one color, a color image that is inverted with respect to the black channel image; and
modifying a color channel in the selected location to accommodate the color image.

24. The method of claim 23, wherein the first image comprises machine-readable indicia.

25. The method of claim 23, wherein modifications in the black channel that correspond to the black channel image reduce at least some visible artifacts that are attributable to modifications in the color channel that correspond to the color image.

26. The method of claim 23, wherein the color channel comprises a red channel.

27. The method of claim 26, further comprising modifying a yellow channel and a blue channel in the selected location to accommodate the color image.

28. A method of providing digital watermarking comprising:

providing a first color on a first surface, wherein the first color includes first modifications corresponding to first digital watermarking; and
providing a second color on the first surface, wherein the second color is different than the first color, and wherein the second color includes second modifications corresponding to second digital watermarking, and wherein the first modifications and the second modifications cooperate to reduce perceptibility of the first and second digital watermarking on the first surface.

29. The method of claim 28, wherein the first color comprises a spot color.

30. The method of claim 29, wherein the second color comprises a black color.

31. A printed article resulting from the method of claim 28.

32. A printed article resulting from the method of claim 29.

33. A printed article resulting from the method of claim 30.

34. A method of providing digital watermarking comprising:

providing a first color on a first surface; and
providing a second color that is different than the first color on the first surface, wherein the second color includes modifications corresponding to digital watermarking, and wherein the modifications are at least partially obscured from human perception by at least some portions of the first color.

35. The method of claim 34, wherein the first color comprises a spot color and the second color comprises a black color.

36. The method of claim 34, wherein the portions of the first color comprise modifications corresponding to digital watermarking, and wherein the first color modifications and the second color modifications offset one another in at least some respects so as to reduce visual artifacts that would otherwise be attributable to the digital watermarking.

37. A printed article resulting from the method of claim 34.

38. A printed article resulting from the method of claim 35.

39. A printed article resulting from the method of claim 36.

Referenced Cited
U.S. Patent Documents
4238849 December 9, 1980 Gassmann
4504084 March 12, 1985 Jauch
4725462 February 16, 1988 Kimura
4739377 April 19, 1988 Allen
5051835 September 24, 1991 Bruehl et al.
5093147 March 3, 1992 Andrus et al.
5228056 July 13, 1993 Schilling
5291243 March 1, 1994 Heckman et al.
5337361 August 9, 1994 Wang et al.
5363212 November 8, 1994 Taniuchi et al.
5385371 January 31, 1995 Izawa
5450490 September 12, 1995 Jensen et al.
5481377 January 2, 1996 Udagawa et al.
5510900 April 23, 1996 Shirochi et al.
5530751 June 25, 1996 Morris
5530759 June 25, 1996 Braudaway et al.
5557412 September 17, 1996 Saito et al.
5568555 October 22, 1996 Shamir
5617119 April 1, 1997 Briggs et al.
5621810 April 15, 1997 Suzuki et al.
5636874 June 10, 1997 Singer
5646997 July 8, 1997 Barton
5652626 July 29, 1997 Kawakami et al.
5659628 August 19, 1997 Tachikawa et al.
5659726 August 19, 1997 Sandford et al.
5661574 August 26, 1997 Kawana
5687236 November 11, 1997 Moskowitz et al.
5689623 November 18, 1997 Pinard
5696594 December 9, 1997 Saito et al.
5721788 February 24, 1998 Powell et al.
5748763 May 5, 1998 Rhoads
5760386 June 2, 1998 Ward
5787186 July 28, 1998 Schroeder
5788285 August 4, 1998 Wicker
5790693 August 4, 1998 Graves et al.
5790703 August 4, 1998 Wang
5809139 September 15, 1998 Girod et al.
5822436 October 13, 1998 Rhoads
5825892 October 20, 1998 Braudaway et al.
5832186 November 3, 1998 Kawana
5838814 November 17, 1998 Moore
5857038 January 5, 1999 Owada et al.
5862218 January 19, 1999 Steinberg
5862260 January 19, 1999 Rhoads
5875249 February 23, 1999 Mintzer et al.
5893101 April 6, 1999 Balogh et al.
5905800 May 18, 1999 Moskowitz et al.
5905819 May 18, 1999 Daly
5915027 June 22, 1999 Cox et al.
5919730 July 6, 1999 Gasper et al.
5930369 July 27, 1999 Cox et al.
5933798 August 3, 1999 Linnartz
5946414 August 31, 1999 Cass et al.
5951055 September 14, 1999 Mowry, Jr.
5960081 September 28, 1999 Vynne et al.
5960103 September 28, 1999 Graves et al.
5974548 October 26, 1999 Adams
5978013 November 2, 1999 Jones et al.
6045656 April 4, 2000 Foster et al.
6046808 April 4, 2000 Fateley
6054021 April 25, 2000 Kurrle et al.
6081827 June 27, 2000 Reber et al.
6094483 July 25, 2000 Fridrich et al.
6104812 August 15, 2000 Koltai et al.
6122403 September 19, 2000 Rhoads
6128411 October 3, 2000 Knox
6136752 October 24, 2000 Paz-Pujalt et al.
6185312 February 6, 2001 Nakamura et al.
6185683 February 6, 2001 Ginter et al.
6192138 February 20, 2001 Yamadaji
6201879 March 13, 2001 Bender et al.
6226387 May 1, 2001 Tewfik et al.
6233347 May 15, 2001 Chen et al.
6233684 May 15, 2001 Stefik et al.
6234537 May 22, 2001 Gurmann et al.
6246777 June 12, 2001 Agarwal et al.
6272176 August 7, 2001 Srinivasan
6272248 August 7, 2001 Saitoh et al.
6272634 August 7, 2001 Tewfik et al.
6278792 August 21, 2001 Cox et al.
6281165 August 28, 2001 Cranford
6285776 September 4, 2001 Rhoads
6286036 September 4, 2001 Rhoads
6304345 October 16, 2001 Patton et al.
6314192 November 6, 2001 Chen et al.
6320675 November 20, 2001 Sakaki et al.
6332031 December 18, 2001 Rhoads et al.
6332194 December 18, 2001 Bloom et al.
6334187 December 25, 2001 Kadono
6356363 March 12, 2002 Cooper et al.
6373965 April 16, 2002 Liang
6374036 April 16, 2002 Ryan et al.
6390362 May 21, 2002 Martin
6394358 May 28, 2002 Thaxton et al.
6398245 June 4, 2002 Gruse et al.
6404926 June 11, 2002 Miyahara et al.
6418232 July 9, 2002 Nakano et al.
6425081 July 23, 2002 Iwamura
6427012 July 30, 2002 Petrovic
6427020 July 30, 2002 Rhoads
6438251 August 20, 2002 Yamaguchi
6449367 September 10, 2002 Van Wie et al.
6456393 September 24, 2002 Bhattacharjya et al.
6456726 September 24, 2002 Yu et al.
6481753 November 19, 2002 Van Boom et al.
6546114 April 8, 2003 Venkatesan et al.
6574348 June 3, 2003 Venkatesan et al.
6590996 July 8, 2003 Reed et al.
6614914 September 2, 2003 Rhoads et al.
6636638 October 21, 2003 Yamaguchi
20010014169 August 16, 2001 Liang
20010021144 September 13, 2001 Oshima et al.
20010024510 September 27, 2001 Iwamura
20010026377 October 4, 2001 Ikegami
20010026618 October 4, 2001 Van Wie et al.
20010028727 October 11, 2001 Naito et al.
20010030759 October 18, 2001 Hayashi et al.
20010030761 October 18, 2001 Ideyahma
20010033674 October 25, 2001 Chen et al.
20010037313 November 1, 2001 Lofgren et al.
20010037455 November 1, 2001 Lawandy et al.
20010040980 November 15, 2001 Yamaguchi
20010047478 November 29, 2001 Mase
20010051996 December 13, 2001 Cooper et al.
20010052076 December 13, 2001 Kadono
20010053235 December 20, 2001 Sato
20010054644 December 27, 2001 Liang
20020015509 February 7, 2002 Nakamura et al.
20020018879 February 14, 2002 Barnhart et al.
20020021824 February 21, 2002 Reed et al.
20020023218 February 21, 2002 Lawandy et al.
20020027612 March 7, 2002 Brill et al.
20020027674 March 7, 2002 Tokunaga et al.
20020031241 March 14, 2002 Kawaguchi et al.
20020033844 March 21, 2002 Levy et al.
20020040433 April 4, 2002 Kondo
20020057431 May 16, 2002 Fateley et al.
20020061121 May 23, 2002 Rhoads et al.
20020061122 May 23, 2002 Fujihara et al.
20020062442 May 23, 2002 Kurahashi
20020064298 May 30, 2002 Rhoads et al.
20020064759 May 30, 2002 Durbin et al.
20020067844 June 6, 2002 Reed et al.
20020067914 June 6, 2002 Schumann et al.
20020068987 June 6, 2002 Hars
20020073317 June 13, 2002 Hars
20020080396 June 27, 2002 Silverbrook et al.
20020083123 June 27, 2002 Freedman et al.
20020090112 July 11, 2002 Reed et al.
20020097873 July 25, 2002 Petrovic
20020097891 July 25, 2002 Hinishi
20020099943 July 25, 2002 Rodriguez et al.
20020106192 August 8, 2002 Sako
20020112171 August 15, 2002 Ginter et al.
20020114458 August 22, 2002 Belenko et al.
20020118394 August 29, 2002 McKinley et al.
20020122566 September 5, 2002 Keating et al.
20020122567 September 5, 2002 Kuzmich et al.
20020122568 September 5, 2002 Zhao
20020126842 September 12, 2002 Hollar
20020126869 September 12, 2002 Wang et al.
20020141310 October 3, 2002 Stephany et al.
20020150239 October 17, 2002 Carny et al.
20020150246 October 17, 2002 Ogino
20020158137 October 31, 2002 Grey et al.
20020163633 November 7, 2002 Cohen
20020164051 November 7, 2002 Reed et al.
20020164052 November 7, 2002 Reed et al.
20020168082 November 14, 2002 Razdan
20020168087 November 14, 2002 Petrovic
20020170966 November 21, 2002 Hannigan et al.
20020176600 November 28, 2002 Rhoads et al.
20020178368 November 28, 2002 Yin et al.
20020181732 December 5, 2002 Safavi-Naini et al.
20030005304 January 2, 2003 Lawandy et al.
20030009669 January 9, 2003 White et al.
20030012562 January 16, 2003 Lawandy et al.
20030032033 February 13, 2003 Anglin et al.
20030056104 March 20, 2003 Carr et al.
20030081779 May 1, 2003 Ogino
20030081857 May 1, 2003 Tapson
20030088775 May 8, 2003 Weimerskirch
20030098345 May 29, 2003 Kobayashi et al.
20030101141 May 29, 2003 Iwamura
Foreign Patent Documents
2943436 May 1981 DE
590884 April 1994 EP
642060 March 1995 EP
705022 April 1996 EP
991047 April 2000 EP
1077570 February 2001 EP
1137244 September 2001 EP
1152592 November 2001 EP
1173001 January 2002 EP
1209897 May 2002 EP
1534403 December 1978 GB
2360659 September 2001 GB
07093567 April 1995 JP
07108786 April 1995 JP
WO9513597 May 1995 WO
WO9603286 February 1996 WO
WO0105075 January 2001 WO
WO0108405 February 2001 WO
WO0139121 May 2001 WO
WO0172030 September 2001 WO
WO0173997 October 2001 WO
WO0197128 December 2001 WO
WO0197175 December 2001 WO
WO0207425 January 2002 WO
WO0207442 January 2002 WO
WO0217631 February 2002 WO
WO0219269 March 2002 WO
WO0219589 March 2002 WO
WO0221846 March 2002 WO
WO0223481 March 2002 WO
WO02056264 July 2002 WO
WO0188883 November 2002 WO
WO02098670 December 2002 WO
Other references
  • Chae et al. “Color Image Embedding using Multidimensional Lattice Structures”, University of California, IEEE 1998, pp. 460-464.*
  • U.S. Appl. No. 60/082,228, filed Apr. 16, 1998, Rhoads.
  • U.S. Appl. No. 09/433,104, filed Nov. 3, 1999, Rhoads et al.
  • U.S. Appl. No. 09/465,418, filed Dec. 16, 1999, Rhoads et al.
  • U.S. Appl. No. 09/503,881, filed Feb. 14, 2000, Rhoads et al.
  • U.S. Appl. No. 09/553,084, filed Apr. 19, 2000, Reed et al.
  • U.S. Appl. No. 09/562,516, filed May 1, 2000, Rodriguez et al.
  • U.S. Appl. No. 09/619,264, filed Jul. 19, 2000, Kumar.
  • U.S. Appl. No. 09/694,465, filed Oct. 23, 2000, Rodriguez et al.
  • U.S. Appl. No. 60/323,148, filed Sep. 17, 2001, Davis et al.
  • Alattar, “‘Smart Images’ Using Digimarc's Watermarking Technology,” IS&T/SPIE's 12th Int. Symposium on Electronic Imaging, San Jose, CA, Jan. 25, 2000, vol. 3971, No. 25, 10 pages.
  • Battialo et al., “Robust Watermarking for Images Based on Color Manipulation,” IH/99 LNCS 1768, pp. 302-317,2000.
  • Bender et al., “Applications for Data Hiding,” IBM Systems Journal, vol. 39, Nos 3&4, 2000, pp. 547-568.
  • Bors et al., “Image Watermarking Using DCT Domain Constraints,” Proc. Int. Conf. on Image Processing, vol. 3, pp. 231-234.
  • Brownell, “Counterfeiters Dye Over Security Measures,” SPIE's OE Magazine, Sep. 2001, pp. 8-9.
  • Fleet et al., “Embedding Invisible Information in Color Images,” Proc. Int. Conf. on Image Processing, vol. 1, pp. 532-535, Oct., 1997.
  • Frequently Asked Questions About Digimarc Signature Technology, Aug. 1, 1995, http://www.digimarc.com, 9 pages.
  • “Holographic signatures for digital images,” The Seybold Report on Desktop Publishing, Aug. 1995, one page.
  • Hunt, “The Reproduction of Colour in Photography, Printing & Television,” 1987, pp. 588, 589 and Plate 35 (in color).
  • Kohda et al., “Digital Watermarking Through CDMA Channels Using Spread Spectrum Techniques,” 2000 IEEE, pp. 671-674.
  • Komatsu et al., “A Proposal on Digital Watermark in Document Image Communication and Its Application to Realizing a Signature,” Electronics and Communications in Japan, Part 1, vol. 73, No. 5, 1990, pp. 22-33.
  • Komatsu et al., “Authentication System Using Concealed Image in Telematics,” Memoirs of the School of Science & Engineering, Waseda Univ., No. 52, 1988, pp. 45-60.
  • Kutter et al., “Digital Signature of Color Images Using Amplitude Modulation,” SPIE vol. 3022, 1997, pp. 518-526.
  • ORuanaidh et al, “Watermarking Digital Images for Copyright Protection,” http://www.kalman.mee.tcd.ie/people/jjr/eva_pap.html, Feb. 2, 1996, 8 pages.
  • Piva et al., “Exploiting the Cross-Correlation of RGB-Channels for Robust Watermarking of Color Images,” 1999 IEEE, pp. 306-310.
  • Vidal et al., “Non-Noticeable Information Embedding in Color Images: Marking and Detection,” IEEE (1999), pp. 293-297.
  • Voyatzis et al., “Embedding Robust Watermarks by Chaotic Mixing,” Digital Signal Processing Proceedings, IEEE Jul. 1977, pp. 213-216, vol. 1.
  • Wang et al., “Embedding Digital Watermarks in Halftone Screens,” Security and Watermarking of Multimedia Contents II, Proc. of SPIE vol. 3971 (2000), pp. 218-227.
Patent History
Patent number: 6891959
Type: Grant
Filed: Apr 2, 2002
Date of Patent: May 10, 2005
Patent Publication Number: 20020168085
Assignee: Digimarc Corporation (Beaverton, OR)
Inventors: Alastair M. Reed (Lake Oswego, OR), Trent J. Brundage (Tigard, OR)
Primary Examiner: Kanjibhai Patel
Attorney: Digimarc Corporation
Application Number: 10/115,444
Classifications
Current U.S. Class: Applications (382/100); Color Image Processing (382/162)